可连接Observable队列除了在被订阅时不发送元素之外都和普通的Observable队列类似，作为替代可连接的Observable队列只在他们的connect()方法执行后才会发送元素。所以你可以订阅所有你想订阅的连接型OBservable队列在他发送元素之前。
这个页面里的所有例子都有注释掉的代码，试着去掉这些注释重新运行观察结果，然后再把注释添加回来 。
在开始学习可连接队列前我们来回顾一下不可连接队列的操作:
func sampleWithoutConnectableOperators() {
printExampleHeader(#function)
let interval = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
_ = interval
.subscribe(onNext: { print("Subscription: 1, Event: \($0)") })
delay(5) {
_ = interval
.subscribe(onNext: { print("Subscription: 2, Event: \($0)") })
}
}
//sampleWithoutConnectableOperators() // ⚠️ 去掉这些注释重新运行观察结果，然后再把注释添加回来.
interval创建一个在每个周期(Period)后发送元素的Observable队列. 更多信息
把元Observable队列转换成可连接的Observable队列。 更多信息
func sampleWithPublish() {
printExampleHeader(#function)
let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
.publish()
_ = intSequence
.subscribe(onNext: { print("Subscription 1:, Event: \($0)") })
delay(2) { _ = intSequence.connect() }
delay(4) {
_ = intSequence
.subscribe(onNext: { print("Subscription 2:, Event: \($0)") })
}
delay(6) {
_ = intSequence
.subscribe(onNext: { print("Subscription 3:, Event: \($0)") })
}
}
//sampleWithPublish() // ⚠️ 去掉这些注释重新运行观察结果，然后再把注释添加回来.
> 执行操作的调度者只是一个抽象出来的概念，比如在指定线程和`dispatch queues`。 [更多信息](https://github.com/ReactiveX/RxSwift/blob/master/Documentation/Schedulers.md)把原Observable队列转换为可连接队列。并把bufferSize大小的之前元素推送给新的订阅者。 更多信息
func sampleWithReplayBuffer() {
printExampleHeader(#function)
let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
.replay(5)
_ = intSequence
.subscribe(onNext: { print("Subscription 1:, Event: \($0)") })
delay(2) { _ = intSequence.connect() }
delay(4) {
_ = intSequence
.subscribe(onNext: { print("Subscription 2:, Event: \($0)") })
}
delay(8) {
_ = intSequence
.subscribe(onNext: { print("Subscription 3:, Event: \($0)") })
}
}
// sampleWithReplayBuffer() // ⚠️ 去掉这些注释重新运行观察结果，然后再把注释添加回来.转化原Observable队列为可连接队列，并发送指定的Subject。
func sampleWithMulticast() {
printExampleHeader(#function)
let subject = PublishSubject<Int>()
_ = subject
.subscribe(onNext: { print("Subject: \($0)") })
let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
.multicast(subject)
_ = intSequence
.subscribe(onNext: { print("\tSubscription 1:, Event: \($0)") })
delay(2) { _ = intSequence.connect() }
delay(4) {
_ = intSequence
.subscribe(onNext: { print("\tSubscription 2:, Event: \($0)") })
}
delay(6) {
_ = intSequence
.subscribe(onNext: { print("\tSubscription 3:, Event: \($0)") })
}
}
//sampleWithMulticast() // ⚠️ 去掉这些注释重新运行观察结果，然后再把注释添加回来.